1. Field of the Invention
The present invention relates to a data processing apparatus for decoding encoded data.
2. Related Background Art
In the modified Huffmann code (MH code) by the modified Huffmann system which is one of one-dimension encoding systems, a punctuation of one main scan line is represented by an end of line code (EOL code). Accordingly, in the MH code or the MR code, the start of next main scan line can be recognized by the EOL code, and it may be readily defined by the EOL code to make white a start pixel at the start of decoding of the main scan line. Thus, in decoding the MH code, the start of the next line can be readily recognized even if the decoding of the code and the development of the code are parallelly executed.
However, the code (MR code) by the modified Reed system which is a two-dimensional encoding system includes line data without EOL code, and the code (MMR code) by the modified modified Reed system does not include the EOL code unlike the MH code.
On the other hand, in the MR code and the MMR code, a code which represents a pass mode is constant without regard to a color of a starting pixel, but a run-length code (RL code) following a horizontal mode changes depending on the color of the starting pixel. When the decoding of one main scan line is completed and the decoding of the next main scan line is to be started, the starting pixel must forcibly defined as white.
As a result, when the RL code following the horizontal mode is to be analyzed, the lines appear in the order of black and white if the line continue from the previous codes in the course of decoding of the main scan line, but they may appear in the order of white and black depending on the development by a developing unit.
Accordingly, in the decoding of the MR code or the MMR code, a code analyzing unit and a developing unit are alternately activated to reflect the development by the developing unit and the code analysis. However, because of the alternate activation of the analyzing unit and the developing unit the decoding time is long.
U.S. Pat. No. 4,750,043 discloses the decoding of a two-dimension code but no proposal to solve the above problem has been made.